1. Field of the Invention
This invention relates to gases distribution systems and in particular, though not solely, to respiratory humidifier systems which humidify gases for a patient, or other person in need of such gases, to breathe.
2. Description of the Prior Art
Many, if not all, existing respiratory humidification systems which deliver humidified gases (such as oxygen or anaesthetic gases) to a patient, or other person in need of such gases, operate as temperature controllers. That is, the temperature of the gases leaving the humidification device in the breathing circuit is monitored and the heat source controlled in response to changes in that temperature to achieve a desired outgoing humidified gases temperature. An example of this type of humidifier control system is disclosed in our prior U.S. Pat. No. 5,558,084. This method of control has a number of disadvantages including:
In situations with high incoming gases temperature (approaching the desired outgoing gases temperature) little heat is necessarily supplied to the gases by the humidification process to achieve the required temperature. Accordingly, little humidification of the gases is also achieved. PA1 The dependency on temperature sensors in this control method means that incorrect placement or connection of the temperature sensors can lead to impaired performance of the entire humidification and breathing system. PA1 Lack of flow sensors which, if provided, would enable certain breathing circuit conditions to be easily recognised and appropriate action to be taken by the humidification device (and/or the gases supply). Flow sensors have previously not been utilised in humidification systems due to insufficient robustness and problems of condensation occurring on the flow sensor, leading to incorrect flow readings. PA1 Gases being supplied to the patient at a pressure/humidity combination which is inappropriate. It is well known that certain humidity levels are required of gases which are to be administered to a patient. Different humidity values are specifically suitable to intact (for example face mask) or bypassed (intubation delivery of gases) airways. Temperature sensing alone can not ensure that these required temperature/humidity values are achieved. PA1 Some existing respiratory humidification devices require users to adjust dials which have little or no intuitive relationship to the actual physical parameters they are intended to control. Often the dials adjust the required gases outlet temperature and/or the heating supplied by the heater wire provided within the conduit connecting humidifier to patient (and sometimes also the conduit connecting the patient back to the gases supply). The most important parameter in humidified gases supply to a patient is the humidity of the gases as insufficient humidity can very quickly dehydrate the patient's airways. Accordingly, users have little or no idea where to position the dials to produce the desires result of optimum humidity in the supplied gases at the existing flow rate. An automated system in which the user need only inform the humidification device if the patient receiving the humidified gases has intact or by-passed airways would be a major advance. PA1 Many existing respiratory humidification devices display the gases temperature being supplied to the patient. As previously mentioned, the most important parameter in respiratory humidification systems is the humidity of the gases. Often, the temperature displayed has no relationship to the actual humidity of the gases being supplied to the patient due to heating in the delivery circuit and can therefore be misleading to the average health care professional. It would, therefore, be an advantage if the temperature displayed was in some way related to or indicative of the humidity of the gases being supplied to the patient. PA1 sensor housing means adapted for positioning in said gases flow, said sensor housing means having a longitudinal axis substantially perpendicular to said humidified gases flow and a sensing end, PA1 sensing means housed within said sensor housing means at or near said sensing end, and PA1 at least one projecting tab means extending laterally from said sensor housing means, said at least one projecting tab means providing surfaces which enable liquid condensate to disperse away from said sensing end of said sensor housing means. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 flow probe means adapted to sense the flow rate of said gases flow, PA1 temperature sensing means adapted to sense the temperature of said gases flow, PA1 user input means to allow a user to set a required temperature of said gases flow, PA1 control means which receives input from said flow probe means, said temperature sensing means and said user input means and control said heating means in response to said inputs to maintain said gases flow at said required temperature. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, said heating means utilising a measurable quantity of power, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 flow probe means adapted to sense the flow rate of said gases flow, PA1 control means which receives input from said flow probe means and storing a program which causes the control means to: PA1 humidification chamber means adapted to hold a quantity of water and having PA1 an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 flow probe means adapted to sense the flow rate of said gases flow, PA1 temperature sensing means adapted to sense the temperature of said gases flow, PA1 user input means to allow a user to select a desired gases humidity level of said gases flow, PA1 data storage means containing information on target gases temperatures at various gases flow rates for a number of humidification chamber outlet means temperatures, PA1 control means which receives input from said temperature sensing means and said user input means and using said flow information from said flow probe means repeatedly obtains corresponding target temperature information from said data storage means corresponding to the desired gases humidity level and varies the heat provided by said heating means until the sensed temperature is substantially equivalent to said target temperature in order to obtain said desired gases humidity level. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 flow probe means adapted to sense the flow rate of said gases flow, PA1 temperature sensing means adapted to sense the temperature of said gases flow, PA1 user input means which may be in one of a predetermined number of states corresponding to one of a number of gases delivery configurations, each configuration optimally requiring a predetermined gases temperature and humidity level, PA1 control means which receives input from said flow probe means, said temperature sensing means and said user input means and controls said heating means to provide said gases flow to said patient or other person in need of such gases at a temperature and humidity level as indicated by said user input means. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, said gases transportation pathway means having a patient end, distal to said end connected to said outlet of said humidification chamber means, PA1 first temperature sensing means adapted to sense the temperature of said gases flow substantially at said outlet of said humidification chamber means, PA1 second temperature sensing means adapted to sense the temperature of said gases flow substantially at said patient end of said gases transportation pathway means, PA1 display means adapted to display temperature information to a user, PA1 control means which receives input from said first temperature sensing means and outputs a signal to said display means to cause a temperature to be displayed to the user which is the lower of the temperatures sensed by said first and said second temperature sensing means. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 flow probe means adapted to sense the flow rate of said gases flow, and PA1 control means which receives input from said flow probe means and compares the sensed flow rate of said gases flow with a predetermined minimum required gases flow rate and places the humidification apparatus into a safe mode of operation if the sensed rate is less than said predetermined minimum rate. PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, said gases transportation pathway means having a patient end, distal to said end connected to said outlet of said humidification chamber means, PA1 humidity sensing means which senses the humidity of said gases flow being supplied to said patient, PA1 timer means which may be used to time certain humidification apparatus events, PA1 alarm means which may be energised to provide a warning signal after a predetermined alarm time, PA1 storage means which stores said alarm times for a number of associated sensed humidity values, and PA1 control means which stores a program which causes the control means to: PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, PA1 heating means power utilisation sensing means which monitors the level of power being used by said heating means, PA1 heating means temperature sensing means which senses the temperature of said heating means, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, said gases transportation pathway means having a patient end, distal to said end connected to said outlet of said humidification chamber means, PA1 alarm means which may be energised to provide a warning signal after a predetermined alarm time, and PA1 control means which stores a program which causes the control means to: PA1 humidification chamber means adapted to hold a quantity of water and having an inlet and an outlet to allow said gases flow to pass through said humidification chamber means, PA1 heating means provided adjacent said humidification chamber means and adapted to provide heat to said quantity of water in said humidification chamber means in order to provide water vapour to said gases flow passing through said humidification chamber means, said heating means utilising a measurable quantity of power, PA1 gases transportation pathway means connected to said outlet of said humidification chamber means to convey said gases flow to said patient or other person in need of such gases, PA1 gases transportation pathway heating means which are energisable to supply heat to said gases flow along at least a part of the length of said gases transportation pathway means, PA1 gases temperature sensing means which senses the temperature of said gases flow leaving said humidification chamber means, PA1 user input means to allow a user to enter a required temperature offset value which is the required difference in temperature between the said sensed gases temperature and the temperature of the gases flow delivered to said patient, PA1 control means which stores a program which causes the control means to: